1. Field of the Invention
The present invention relates to an improved touch signal probe which can accurately detect the motion of a pin contacting a work equally in multi-axis directions.
2. Prior Art
Three-dimensional coordinate measuring systems are currently utilized in the field of precise measurement since they can accurately effect the three-dimensional measurement of works having complicated shapes which are placed on a base and contacted by a probe.
In such a type of measuring machines, a movable probe is manually or automatically moved in three-dimensional directions to contact a work at given points of measurement whereat the coordinates of the probe moved in each of the three axes are read out. Recently, a touch signal probe is broadly used which is adapted to automatically detect electrical touch signals indicative of contact with a work. Such a probe can automatically be moved and measure works of complicated configurations.
In general, the touch signal probe includes a touch pin adapted to contact a work, the touch pin being movably supported by a probe case. The touch signal probe also includes means for absorbing the displacement of the touch pin on contacting the work and contact means located between the contact pin and the work or on the supporting mechanism for the touch pin.
In the prior art touch signal probes, however, the contact means is supported on the supporting portion for the touch pin at three points so that measurements will depend on the axis directions. Thus, stabilized measurements cannot be obtained in all directions. Such directional errors cannot be corrected in the prior art.
Instead of the above contact type probe, there has been proposed a probe which electrically detects the angular position or motion of a touch pin as by the use of a differential transformer. Indeed, such a differential transformer type probe cannot have a good sensitivity of detection. Particularly, the sensitivity of detection thereof is directional with respect to the movement of the touch pin.